This investigation will continue our characterization of the surface antigens of Streptococcus mutans in order to provide the basis for formulating an anticaries vaccine. Since serotypes c and d are the most common among humans, the study will emphasize serotype c antigen and the crossreacting rhamnose-glucose antigens from serotypes d and g. Specifically, the aims are: (1) to elucidate the physico-chemical structure of the wall-associated carbohydrate antigens of S. mutans and of the specific determinants on these antigens; (2) to develop immunogenic complexes with the lipidesterified serotype c polysaccharide; and (3) to examine the protective effects of the polysaccharide immunogens in the hamster caries model. The polysaccharide structures will be elucidated by gas-chromatography/mass spectroscopy (GC/MS) analysis of their methylated and periodate oxidized/methylated derivatives. Identification of specific determinants on the antigens will utilize small saccharides chromatographically purified from acid hydrolysates. These saccharides will be examined structurally by GC/MS and immunologically by quantitative inhibition assays. Complexes of lipid-esterified polysaccharides will be examined for their immunogenic properties in hamsters and rabbits. Studies will focus on palmitoyl-c antigen incorporated into liposomes in the presence or absence of additional adjuvants, i.e. stearoyl-muramyl- dipeptide, polylysine, and vitamin A. Both systemic and oral routes of immunization will be utilized. Specific immunoglobulin responses will be examined using the enzyme-linked immunosorbant assay (ELISA) with c polysaccharide as antigen. Polysaccharide complexes that are determined to be immunogenic will be examined for their caries protective value in hamsters. Both initial oral colonization by S. mutans and caries development will be examined. Caries will be scored by Keyes' method. Rabbit antisera that is specific for c polysaccharide will be tested for crossreactivity with extracts of human tissue by the ELISA and comparative immunoelectrophoresis methods. This is an essential assay in determining the safety of developing a polysacharide vaccine to S. mutans for human use.